Localized state and charge transfer in nitrogen-doped graphene

TL;DR

This study investigates nitrogen-doped graphene grown on SiC, revealing how nitrogen atoms substitute carbon, induce charge transfer, and create localized energy levels, with implications for electronic properties.

Contribution

It provides detailed atomic-scale characterization of nitrogen doping configurations and their electronic effects in epitaxial graphene, supported by experimental and theoretical analysis.

Findings

Nitrogen substitution reduces local charge density on nitrogen sites.

Localized energy levels associated with nitrogen doping are observed in conduction band.

Various nitrogen-related defects exhibit complex structures and hole-doping effects.

Abstract

Nitrogen-doped epitaxial graphene grown on SiC(000?1) was prepared by exposing the surface to an atomic nitrogen flux. Using Scanning Tunneling Microscopy (STM) and Spectroscopy (STS), supported by Density Functional Theory (DFT) calculations, the simple substitution of carbon by nitrogen atoms has been identified as the most common doping configuration. High-resolution images reveal a reduction of local charge density on top of the nitrogen atoms, indicating a charge transfer to the neighboring carbon atoms. For the first time, local STS spectra clearly evidenced the energy levels associated with the chemical doping by nitrogen, localized in the conduction band. Various other nitrogen-related defects have been observed. The bias dependence of their topographic signatures demonstrates the presence of structural configurations more complex than substitution as well as hole-doping.